no, I don't recommend installing anything on the host. Do it all in a Container.
I'm using awscli (1) which allows me to synchronise, in a similar way as rsync, the backup files created by Proxmox using vzbackup.
The Container has access to these files using a bindmount.
Why not install awscli on the host itself? Because it uses all sorts of Python stuff. You don't want to be adding unexpected and potentially conflicting things to the host node. That's what Containers are for, after all.